Epdm Rubber Compound
EPDM Chemistry and Compound Preparation
Ethylene-propylene elastomers share the same monomers as thermoplastic polymers polyethylene (PE) and polypropylene (PP). Depending on the polymer composition and how individual monomers are combined, ethylene-propylene rubbers can be produced in a wide range from amorphous, non-crystalline structures to semi-crystalline structures. These polymers can also be produced over a broad Mooney viscosity range.
When compounded and blended, the ethylene and propylene monomers in EPDM form a chemically saturated, stable backbone, providing excellent resistance to ozone, heat, oxidation, and weathering. From here, a third unsaturated diene monomer can be terpolymerized to provide reactive unsaturation in the side chain while maintaining the saturated backbone of the polymer, making it suitable for vulcanization or polymer modification chemistry. The resulting terpolymers are referred to as EPDM.
When compounded and blended, the ethylene and propylene monomers in EPDM form a chemically saturated, stable backbone, providing excellent resistance to ozone, heat, oxidation, and weathering. From here, a third unsaturated diene monomer can be terpolymerized to provide reactive unsaturation in the side chain while maintaining the saturated backbone of the polymer, making it suitable for vulcanization or polymer modification chemistry. The resulting terpolymers are referred to as EPDM.
EPDM Rubber Material Properties
General Properties
| Durometer Range (Shore A) | 30-90 |
| Tensile Strength Range (P.S.I) | 500-2500 |
| Elongation (Max %) | 600 |
| Compression Set | Good |
| Flexibility – Rebound | Good |
| Abrasion Resistance | Good |
| Tear Resistance | Moderate |
| Solvent Resistance | Poor |
| Oil Resistance | Poor |
| Low-Temperature Use (F°) | -20° to -60° |
| High-Temperature Use (F°) | Up to 350° |
| Weather Resistance – Sunlight Exposure | Excellent |
| Bonding to Metals | Moderate to Good |
EPDM Elastomer Properties
The different properties of a finished EPDM compound are largely controlled by the ethylene and diene content, Mooney viscosity, and molecular weight distribution.
For example – reducing ethylene content will decrease crystallinity, thus reducing hardness and modulus.
The following table highlights some general properties considered during EPDM compounding and the results of having certain properties at higher or lower levels.
For example – reducing ethylene content will decrease crystallinity, thus reducing hardness and modulus.
The following table highlights some general properties considered during EPDM compounding and the results of having certain properties at higher or lower levels.
| Property | High | Low |
| Ethylene Content | High Flow at Extrusion Temperatures High Tensile Strength, Modulus Good Green Strength High Loading (Cost Reduction) | Fast Mixing, Calendaring, and Milling Low Hardness and Modulus Low-Temperature Flexibility |
| Diene Content | Flexibility in Acceleration High Modulus, Low Set Good Compression Set Cure Rate and Speed | High Heat Stability Low Hardness and Modulus Flame Resistance |
| Molecular Weight | Good Modulus and Set High Loading and Oil Extension Good Green Strength Good Tensile and Tear Resistance Sag Resistance | High Extrusion Rates Low Viscosity, Flame Resistance Good Calendaring Fast Mixing |
| Molecular Weight Distribution (MWD) | Good Overall Processing Sag Resistance Good Milling and Calendaring Extrusion Feed and Smoothness | Fast Extrusion Rate High Cure Low Die Swell Good Physical Properties |
EPDM Rubber Applications
The properties of EPDM make it a highly versatile synthetic rubber, widely used in both specialty and general-purpose applications.
Due to its ability to be processed for different needs, it is used by many industries in various applications such as automotive weather seals, glass run channels, EPDM gaskets, automotive seals, EPDM hoses for radiators, garden, and household appliances, EPDM pipes, electrical insulation, roofing membranes, EPDM belts, and plastic impact modification. It is also widely used in rubber mechanical products, water system O-rings and hoses, ozone exposure applications, and automotive cooling systems.
Due to its ability to be processed for different needs, it is used by many industries in various applications such as automotive weather seals, glass run channels, EPDM gaskets, automotive seals, EPDM hoses for radiators, garden, and household appliances, EPDM pipes, electrical insulation, roofing membranes, EPDM belts, and plastic impact modification. It is also widely used in rubber mechanical products, water system O-rings and hoses, ozone exposure applications, and automotive cooling systems.